Another idea

[Tobias Polzin]

>   TP> But I agree that it is a security problem. The possibility to
>   TP> ruin your backup is always a problem. In the link you send me,
>   TP> this problem is solved in an elegant way.
> 
> The elegant way being that rsync happens never to actually modify any
> file's data...

... and the use of loop-mounting some directories read only...

>   TP> As it seems, that you don't like the idea, I will have to
>   TP> implement it myself. Shall I send you patches that you have it
>   TP> (at least as undocumented feature) and I can more easily
>   TP> incooperate rdiff-backup updates?
> 
> Sure, this would be good.

We just found a different solution (without rdiff-backup). If 
we stay with this, I will not patch rdiff-backup.

>   TP> So, what fraction "mirror files"/"increment files"?
> 
> About 80-85% mirror files in my case.

Ah, thanks.

Tobias